Telephone repeater equipment



C. s. DEMAREST, A. BqCLARKAND G.' cmssw.

TELEPHONE REPEATER EQUIPMENT.

APPLICATION vFILED APR.16. 1919.

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Z SHEETS-SHEE I V .INVENTOR @www / TTORNEY HARLE S. DEMREST, OF NEW 'lt'RIL ANA B. CLARK, IBB'KLYN, tlit't VDRK, AND GtlEGRGE CMSSON, 0F EEIOBDKEN, NEW JERSEY, ASSIGNURS T0 AEl't- CMI 'TELEPHONE AND TELEGRAZPH CUhuTlthl'Y, it CORPRATIDN 0F NEW EMRK.

TELEPHNE REPIETER EQUXPMENT.

aesinet.

Specification ct Letters Yatent.

Patented July Ml, 192i..

Application. tiled llpril N5, 19W. ilerinl lilo. 90,362.

To all whom it 'may concern.'

Be it known that we, CHARLES S. DEMA- iiizsr, Anya BCLARit, and Gnoiioii Caisson, residing at New York, Brooklyn, afiid llobeken, in the counties of New York, Kings,

and Hudson and States of New York, Newv York, and New Jersey, respectively, have invented certain Improvements in' 'lelephone Repeater Equipments, ot' which the followingy is a specification.

This invention relates to transmission circuitsiand more particularly to arrangements whereby an operator may supervise, talk, and ring on transmission circuits which include repeater element-s;

`When a transmission circuit includes re peuter elements the two line sections ot the circuit which are interconnected by the repeater are balanced by artificial lines associated with the repeater. lt a suiiciently high degree ot balance is obtained between the line sections and artificial lines it is possible to prevent singing from taking place over the circuit. The association of equipment for supervision, talking, or ringing with suoli a circuit is apt to cause a degree oi imbalance sufficient to cause singing. lin former arrangements it has been the pracf tice in order to obviate this dili'iculty to disconnect the repeater apparatus from thc circuit whenever an operator, testboard man,l

or repeater attendant desired to talk or ring overthe circuit, and provision was made for supervision by wiring a special series monitoring coil to jacks at each point where it` was desired to listen ou the circuit.

Accordingly it is an object oi the invention to eliminate such undesirable features and to enable the operator, testbonrd man, or repeater attendant to supervise, talk. and ring ou circuits equipped with telephone repeaters in the saine ina-nner as on lines not so equipped. A particular object of the invention is to provide an arrangement whereby thc listening apparatus of an opy Y erators supervising circuit may be associ- 'ated with a section otv a line including repeater apparatus without causing appreciai able imbalance. Another object is to pro vide means whereby an operators talking equipment may be associated with a section vof a line including repeater apparatus withput causing the repeater to sing. A. further object has reference 'to the provision of means whereby a listening operator may apply ringing current to such a line without causin serious imbalance between such a line and its balancing artificial line. These objects as well as others, will beclear from the following detailed description of the drawing and of the operation of the invention. i

lin the drawing Figure l illustrates a' circuit diagram of a preferred term of the arrangements of theinvention, while in the Fig. 2 :is illustrated a modification thereof.

n Fig. 1 of the drawing is shown atransmission line, the sections la, and L2 of which are interconnected by the two-element twoway repeater apparaths iB. The repeater apparatus B is of a well known type, and

peater apparat-us B are artificial lines N,

and N2 adapted to balance the sections L1 and L2 respectively ot' the transmission line. The supervising, talking andv ringing equipnient is associated with the contacts of the key K, which, when thrown in one direction bridges the equipment across section L1 of the line, and when thrown in the other direction bridges the equipment across the.

section L2 of the lino.V By means of conductors 8, v9 and 9', and other conductors (not shown) similar thereto, the supervising operatoi"s equipment may be associate-d with the other keys similar to key K', and

may be used in connection with a plurality of lines. 'lhe supervising equipment is associated with the contacts of key K, through the transformer 6, one winding of which is of sufficiently high impedance, so that,

when the supervising equipment is bridged i across a section of the line, no appreciable unbe-lance will result between the section of the line and its balancing artificial line. Connected. in series with one of the visitl ings of transformer 6 is the high resistance element 7 and the condenser 8, which serve as a filter to attenuate and practically extinguish currents of relatively low frequenr equipment is normally associated with the other winding of transformer 6 by means of-an amplifier A. This amplifier is preferably of the vacuum tube type, in order that it. may draw only an inappreciable amount ofl energy from the line, but at the san .e time will deliver enough energy to produce a proper volume of sound in the receiver. Under these conditions, the only energy drawn from the line is that required to excite the transformer 6, which works with the Secondary effectively open. Betweenv the output winding of the amplifier A and the receiver R is provided a network N including a series resistance and a shunt resistance. These resistances reduce the sound in the receiver to a volume suitable for monitoring purposes, and are proportioned so that substantially the same volume of sound will 'be obtained with either the high or low impedance type of receiver customarily used at the testboard.

Associated with the transformer 6 is the key K2, which when operated, disconnects the supervising apparatus and connects ringing apparatus to the transformer 6. When the key K2 is operated a condenser is bridged about the filtering elements 7 and 8 in transformer 6 to provide a path for the low frequency ringing currents. As the ringing equipment which is -to be bridged across the transmission line lthrough the transformer 6 is of low impedance the condition of balance ofthe line and its artificial line would be materially altered. To avoid this, additionalv impedance is inserted in the s bridge in the form of the resistance elements requirement.

18 and 19. Associated therewith is the autotransformer 20 w "zh, when necessary, is used to increase the voltage of the ringing circuit to a value sufiicient to give the desired current in the line. The resistances 18 and19 serve to increase the impedance of the ringing circuit to a value which will not produce singing of the repeater. They have the lowest value consistent with this The strength of the ringing current is determined by the ratio of the auto-transformer 20. If the voltage of the ringing source is high enough, the autotransformer may be omitted and additional series resistances used to give the desired current. Associated with the sourcefof ring- 111g energy is the filter 21, which is of a type operators talking set across the transmission Y line. The operaion of key 1x2 closes aconf denser bridge about the high impedance filtering elements 7 provide a path for the talking currents. As the operators telephone set is of relatively low impedance, the operation of fkey I a would materially alter the condition of balance of the line and its artificial line.` Acand 8 in transformer 6 to cordingly there is provided in the talking circuit Vbetween the operators set and trans- The 1mfomer 6 an autotransformer 28. pedance of the telephone set is.. stepped up by the autotransformer 28 and further stepped up by transformer 6, sufficiently, so y that, when the telephone set is bridged across the transmission line no serious unbalance of the circuit will result. l

lVith reference to the amplifier A no separate source of potential is provided for the grid, the proper grid potential being maintained by means of the resistance element u s 200 inserted in series in the filament circuit between the filament and the point of con nection of the input transformer. Bridged across the input side of the amplifier is the resistance 44 which is of very high imped ance and which serves to prevent disturbances which would be caused whenever the grid is entirely disconnected from the rest of the circuit by the operation of either of the keys K2 or K3,

The invention may now be more fully understood from the following description of its operation. If the operator desires'` to supervise on one of the sections, such as section L1, of the transmission line,v the key K1 will now` be thrown to the left and the left hand or high impedance winding of transformer 6 will beV bridge across the section Ll-of the line, over conductors 3 and 4, make contaictsof key K1, and thence go vr cenductors" 1. As has bcen,former1y pointed out, this .wind-l ing of transformer 6 includes the high resistance 7 and the condenser 8, which serve to reduce ringing and other low frequency disturbances. The impedance ofthis winding is so high that an inappreciable trans mission loss results'and no appreciable uri-A balance occurs between section L1 of 111e line and the artificial line N1. The eperaing circuit: from ground, make contact oi' key iQ, conductor 5, to' connecting' point 201; from connecting point 201, over the normal contact of key Kw conductor 35,v winding of relay 32 'to battery and ground. rlhe closing of this circuit operates the relay 32. A circuit is also closed from connecting point 201, over conductor 36, winding of r'elay 37 to batteijy and ground, thereby energizing relay 37. The operation of relay 37 closes a circuit from ground and battery, resistance il, conductor 42, contact and armature of relay 37, conductor 43, resistance 200, filament oi amplifier to ground. The `closing of this last circuit`conditions the amplilier A for operation. When the amplier A is conditioned for operation and when the relay 32 is operated, the receiver R of the operators supervision equipment is associated with the right hand winding of transformer 6 and with the transmission line L, as iollows: from the right hand winding of trans' former 6, over conductors 12 and 13, normal contacts of key K2, conductors 1a and 15, normal contactsof key K2, conductors 23 and 24, and thence through amplifier A and over the output circuit or amplifier A, through the left hand winding of transformer 27, thence from the right hand windings of transformer 27, over 'conductors 3() and 31, network N, armatures and contacts of relay 32, over conductors 33, contacts of jack l and plug P to the receiver R.

Should the operator desire :to ring over one ci the sections, such as L1, oi the transmission line, the key K1 will then be thrown to the left and the left hand winding` of transformer 6 bridged across the section L1 oi the line as formerly pointed out. The key K2 will then be thrown. The operation of the key K2 opens at its contacts the formerly traced circuit from the receiver R of the operators monitoringl set to the right hand windin of transformer 6, thereby disconnecting te receiver R from the transformer 6 and the section l), of the transmission line. The operation of the key K2 at its upper make contact closes a condenser bridge over conductors 10 and 11, about the high resistance element 7 and the condenser 8 connected in series with the left hand windings oi transformer 6.. llllhe operation of thev key K2 also, connects a source of ringing-current suitable ioruse over the transmission line to the right hand windings of transformer' 6 as follows: from the right hand windings of transformer `6, c over conductors 12 and 13, make contacts of key K2, otfer the conductors 16 and 17, resistance elements 18 and 19, and thence to the autotransiormer 20 and the filter 21, to the source ot ringing current. The resistance elements 18 and 19'serve to, increase the impedance ot thief circuit suiliciently so that no serious imbalance will occur between the section li, of the line and the artirlcial line Nl. The operation of the key K2 also closes a circuit from ground, over its lower make contacts and over the conductor 22 to apparatus which willstart the ringing arrangements in oper-y ation. It is pointed out that the circuit over which the ringing current is now aplied to the section l, of the transmission ine, includes the auto-transformer 20, whereby the voltage of the ringing apparatus is suiiciently stepped up to give the desired ringing current in the line L, when the resistances 18, 19 are in circuit. By this arrangement the ringing apparatus when bridged aci'css the transmission line will have suhciently high impedance so' that no serious imbalance will occur between the section L, of the line and the artiiicial line N1.

lf the operator desires to talk .over a section, such as the section L2, of the transmission line,the key l, will be thrown to the left and the lett hand winding, of transformer 6 will be bridged across the Section L, of the line as previously Vpointed out. The key K2 will now be thrown. The oper-v ation of the key l, closes a condenser bridge at its upper make contact, over conductors 10 and 1l, about the high impedance elements 7 and 8 in the leit hand winding of transformer G. At its lower normal contact the key K2 when operated will open the circuit formerly traced about the winding of the relay 32, thereby preventing the relay from operating and disconnecting the receiver E from the induction coil 29. rlhe talking apparatus of the operators set upon the operation of the key K2, will now be associated with the right hand windin s of transformer 6 and with the section i. of the line as follows: from the right hand` windings of transformer 6, over conductors 12 and 13, normal contacts of key K2, conductors 14 and 15, make contacts of key K3, conductors 25 and 26, windings of the auto- 110 transformer 28, through the transformer 29,

over conductors 34, contacts of jack J and ,plug P to the operators talking set.- This last mentioned circuit includes the autotransiormer 28, whereby the relatively low impedance of the operators talking set will be stepped up suiiciently so that, when the talking set isbridged across the section la, of the (transmission line, but little transmission loss will result thereover and no serious unbalance will occur between the section L, of the line and the artificial line N11.

ln the F ig. 2 is illustrated a modiiication of the 'arrangements shown in Fig. 1, which terminates in the cord and plug l. `Siniilar reference numerals have been used to denote like parts in both arrangements. The supervising, talking, and ringing equipment is associated with the transmission line by inserting the plug l), in Jacks, such as 3,30

- applied thereto.

jacks J1 and J1, associated with the line. The operator-s supervising set is normally associated with the high impedance trans' former 6 which is of sufficiently high mpcdance so that when bridged across the transmission line it 'will cause very little transmission loss thercover and will cause no appreciable unbalance to exist between the transmission line and its balancing artiicial line. Two ringing keys, K5 and K6, are provided which control relay means whereby the operators supervising set will be disconnected from the transformer 6 and different types of ringing current suitable for use over the transmission line may be Under the control of a talking key K7 are relay means which will disconnect the operators supervising set from the transformer 6 and will connect the operators talking set thereto.

Ifthe operator desires to supervise over a section, such as section L1, of thextransmission line, the plug P1 will. be inserted in the jack J1 and the following circuit will be closed: from ground, contacts of jack J1, and plug P lay 70, to battery and ground. This will operate he relay 70 and will bridge the left hand winding of transformer 6 across the sides of section L1 of the transmission line as follows: from the left hand windings of transformer 6, over conductors 3 and 4,A contacts and armatures of relay 70, conductors 71 and 72, contacts of plug P1 and jack J1, and thence over conductors l to the sides of section L1 of the transmission line.` The receiver R of the operators supervising set is associated with the right hand windings of transformer 6 and with the section L1 of the transmission line as follows: from the right hand windings of transformer 6, over "conductors 59, armatures andvnormal contacts of relay 50, conductors 60, armatures and normal contacts of relay 54, conductors 61, armatures and4 normal contacts v of relay 58, conductors 62, through the ammal contacts-of relay 67, conductors 68, net-` pliiier A, through the transformer 27, nor

work N, conductors 78, contacts of jack J- and plug P, to the receiver R.. Upon the aforementioned operation of relay 7() the following circuit will be closed: from ground, armature and contact of relay 70, conductor 74, winding of relay 75, to battery -and ground. This will operate relay 75 and' close the following circuit: from ground and battery, resistance 76, contact and armature of. relay '75, conductor 77, resistance 200, filament of amplifier A to ground. This will condition the amplifier' A Vfor operation, so that the currents which have been attenuated by the high impedance in the left hand winding offtransformer 6, will be sufli- (iiently amplified to produce the desire volame of sound in the receiver B.

1, conductor 69, winding of re` of the line and the artificial .line N1.

'aground T 1s will operate the relay If the operator desires .to talk over a section, such as section L1, .of the transmisslon line, the plug P1 will be inserted in the-jack J 1 and the relay :70 will operate and bridge tures and bridge a condenser over conductor 10, upper make contact and armature of relay 58, and conductor 11, about the high impedance elements 7 and-8 inthe left hand winding of transformer 6. UponV the operation of key K7 the following circuitwill also be closed: from ground, contact of key K7, conductor 66, winding of relay 67, to battery and ground. This will operate relay 67 which will pull up its armatures and connect the receiverv R' of the operators` monitoring set to he transformer 29. Upon the aforementioned operation of relay 58, the transmitter T of the operators talking set will now be associated with the right hand winding oftransformer 6 and with the section L1 of the line as follows: from the right handwinding -of transformer 6, over conductors 59, armatures and normal contacts of relay 50, conductors 60, armatures and normal contacts of relay 54, conductors 6l, armatures and make contacts of relay A58, conductors 63, auto-transformer 28, con-' former 28, whereby the relatively low impedance of the operators talking set will be stepped up sufficiently to insure that when the talkingV set is bridged across section L1 of the transmission line but little transmission loss will result thereover and no serious imbalance will occur between the section L1 If the operator desires to ring over a section of the line such as the line L1 the plug P1 is inserted in the jack J1 and the left hand winding of transformer 6 will be bridged across the line as formerly pointed out. The operatorvwill now throw either the key K5 or the key K6. If the key K1, is

thrown, the following `circuit will be closed :y

from ground, contactof key K6, conductor 53, windin ,of relay .54, to battery and 54 which at its upper make contact will close a condenser bridge over conductors 10 and 11 about the high impedance elements 7 and 48, included in the left hand` winding of transformer 6. The o eration of the ke K1, will also 'close `a circuit from groun i connut of key )KM-over conductor 56,'to

Leeaeea ments 18 and 19, conductors 55, make contacts and armatures of relay 54, conductors 60, normal contacts of relay 50, conductors 59, to the right hand windings' of transformer 6. lt is pointed out that this" last mentioned circuit over which the ringing current is now applied to the section L, of

. the transmission line, includes the high irnpedance of elements 18 and 19 and also the autotransformer 20, whereby the voltage of the ringing apparatus is sufficiently stepped up to give the required current in the line. By this arrangement the ringing apparatus,

when bridged across the transmission line,

will have suiiiciently high impedance so that but little transmission loss will result over the line and no serious unbalance will occur between the section L, of the line and the artificial line N1. lf the operator should desire to transmit over the line ringing current of a different frequency, such, for example, as ringing current of a frequency of titi 20 cycles, the key K5 would *be thrown. The throwing of the key K5 willo operate the relay 50. rlhe operation of the relay 50 will, in amanner similar to the relay, 54:, close a condenser bridge about the high impedance elements in the left hand winding of transformer 6 and will connect to the right hand windings of transformer 6 a source ot' ringing. current. Included in the conductors leading to this source of ringing current are the resistance elements 711 which serve to give the desired impedance in the lett hand windings of transformer and regulate the amount of ringing Vcurrent transmitted to the line.

While the invention has been disclosed in certain specific arrangements which have been deemed desirable, it is understood that it is capable otembodiment in many and Widely varied forms without departing from the spirit of the invention, as defined in the.

ap ended claims.

at is claimed is:

1. A transmission circuit including lines interconnected bv repeater apparatus, means to balance said lines, an operators telephone Set of low impedance, means to includle said set in a bridge across one otsaid lines, and an autotransformer in said bridge whereby the impedance of said telephone set may be stepped up sufficiently to prevent serious unbala-nce of said line.

2. A transmission circuit including lines interconnected by repeater apparatus,meaus 'to balance said lines, ringing equipment of low impedance, means to 'include said equipment in a bridge across one ot said lines, and an autotransformer in said bridge .whereby the impedance of said ringing equipment may be stepped up suiiiciently to prevent serious unbalance of saidlline.

3. A .transmission circuit including lines interconnected by repeater apparatus,means to balance said lines, operators e uipment of low impedance, means to bri ge said equipment across one of said lines, and an autotransformer associated with said bridge for increasing the impedance of said equipment suiiiciently to prevent appreciable unbalance of said line.

4. A transmission circuit including linesl interconnected by repeater apparatus, means to balance said lines, operators'equipment including a talking set, a listening set, andv ringing apparatus, switching means whereby said equipment may be bridged across one of said lines, and an autotransformer included in said equipment whereby the inipedance of said equipment may be sufficiently increased to prevent serious unbalance of said line.

5. A transmission circuit including lines interconnected by repeater apparatus, means to bala-nce said lines, means to complete a bridge across one of said lines, means to include in said bridge either a talking set, a listening set, or a ringing set, and means in'- dividual to each of said sets operative when one of said sets is' included in said bridge "if, t1.

'iti

to increase the impedance of said bridge sufiiciently. to prevent serious imbalance of said line.

6.. A transmission circuit including lines interconnected by repeater apparatus, means to balance said lines, a circuit adapted to be bridged across one of said linesand includ'- ing elements of suiliciently high impedance to prevent appreciable unbalance of said line, an operatorsylistening set, means to coinplete said bridge circuit through said listen-` ing set, an operators talking set, switching means whereby an auxiliary circuit maybev closed about said high impedance elements and said listening set may be disconnected from' said bridge circuit and said circuit may be completed through said talking set, and means associated with said talking set whereby the impedance ol? said bridge cir- .11

cuit as now completed may be sufficiently increased -to prevent serious unbalance of said seid bridge circuit through said listening theimpedance oysaid bridge circuit maybe Set, an operators talking set, ringing equpsufficiently increased to prevent serious unment, switching means whereby an auxiliary l balance of said line.

circuit may be closed about seid high im- Intestimony whereof We have signed our l 5 pedaneelements and said listening set .may naines tothis specification this 15th day of 15 be disconnected from said bridge circuit and April, 1919.

eeid circuit may be completed through either said talking set or said ringing equip- CHARLES S. DEMAREST. L ment, and means individual to said talking ALVA B. CLARK. l0- set and to said ringing equipment whereby GEORGE CRISSON. 

